Lamp



G. SPERTI 2,065,988

LAMP

Filed Jan. 25, 1932 Patented Dec. 29, 1936 UNITED STATESv LAMP George Sperti, Oovington, Ky., minor to Sperti Lamp Corporation, New York, N. Y., a corporation of Delaware Application January 25, 1932, Serial No. 588,747

13 Claims.

This invention relates to are electrodes for use in lamps of the type combining a source of visible radiation and an arc constituting a source of ultra-violet radiation, or for use in any electric arc lamp.

In the prior application of George Sperti, Serial No. 572,394, filed October 31, 1931, there is disclosed a lamp embodying an outer bulb containing a suitable incandescent filament which provides a source of visible radiation and an inner bulb wherein an arc is established between suitable electrodes in an atmosphere of ionized gas or vapor. The resultant spectrum of such a lamp is that of the incandescent filament having superimposed thereon the spectrum from the arc, the latter providing preferably a substantial amount of energy in the ultra-violet region of the spectrum. By separately enclosing the incandescent filament and the arc in the outer 20 and inner bulbs, the two sources are operated independently of one another under optimum conditions and this makes it possible to operate the lamp successfully at normal house lighting voltages and currents. For such purposes, the lamp must be and is entirely self-contained and requires no external devices for starting the are or for controlling the current.

As described in the aforesaid application, the arc is established between a pair of spaced electrodes, and in order to render the arc self-starting, the electrodes are heated by suitable filaments to cause ionization of the gas or vapor in the arc chamber. In order to assist in the ionization of the gas' or vapor, the electrodes 'preferably embody one or more oxides of materials such as thorium, strontium, barium and the like which on being heated have substantial electronic emission. The emission of electrons, together with the heating of the gas or vapor by the filaments, causes rapid ionization in the arc chamber. It is preferable that the electrodes be of some material which does not evaporate or disintegrate on continued operation of the are, metals such as tungsten and the like being particularly well suited, and when such metals are used the oxides may be coated on the electrodes and the heating filaments enclosed within the electrodes which are made in the form of tubes or sleeves. One difficulty, however, with such an electrode is the tendency of the oxide coating rapidly to disintegrate on continued arc operation, shortening the life of the lamp. Another difliculty is that coatings of such oxides do not adhere tenaciously to tungsten. The oxide coating may readily be applied to metals such as nickel; platinum and the like but nickel is apt to burn out prematurely when utilized for the arcing surface.

One of the objects of the present invention is to provide a novel electrode for use in lamps of the above type or in any electric arc lamp which electrode embodies an arcing surface of tungsten and a portion adjacent said arcing surface which is coated with oxides to assist in starting the arc.

Another object is to provide an electricarc lamp embodying spaced electrodes having arcing surfaces of metals such as tungsten and adjacent portions coated with oxides, said electrodes being so arranged that the arcing'surfaces are closer together than the oxide c atings whereby the are after starting establishes and maintains itself primarily on the arcing surfaces.

A further object is to provide an arc lamp chamber in which the arc electrodes are so arranged and the chamber so shaped as to prevent the formation of a deposit on the walls of the chamber where the arc illumination is most effective.

Several embodiments of the invention are illustrated in the accompanying drawing, but it is to be expressly understood that said drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being bad to the appended claims for this purpose.

In the drawing,

Fig. 1 is a perspective view of a complete lamp embodying the invention;

Fig. 2 is a sectional view through the ultraviolet arc element of said lamp;

Fig. 3 is a sectional view of another form of electrode;

Fig. 4 is a diagrammatic view showing a geometrical arrangement of electrodes which may be embodied in the lamp; and

Fig. 5 is a diagrammatic view showing a further form of lamp chamber and arrangement of electrodes.

Referring now to Figs. 1 and 2, the lamp embodies an outer bulb I mounted in any suitable base 2 which is preferably of the conventional screw type. A standard or stem 3 is sealed in the neck of the bulb I and constitutes the usual means for supporting the various elements within the lamp and for introducing the usual leads 4 and 5 therein. An incandescent filament 8, preferably of tungsten, is supported in the lamp by wires 1 and 8, wire 1 being connected to the lead 4 to supply current-to the filament and both of illustrating one use of electrodesv embodying the invention.

Within the bulb is an inner bulb ll mounted in any suitable manner on the stem 3 as by means of a band l2 and a pair of supports it which are .fused in the stem 3. The inner bulb H is sealed by means of a stem or standard I 4 and contains a quantity of gas such'as neon, argon, etc., or vapor such as mercury or both. An arc is established within the bulb H between spaced electrodes which preferably have the form of tubes or sleeves and as shown in Figs. 1 and 2 are placed end to end in said bulb. As shown particularly in Fig. 2, each of these electrodes comprises a sleeve I! of nickel or like material coated at I 6 with an electron emitting oxide or mixture of these oxides such as thorium, barium, strontium, etc. Over the ends of the sleeves I6 are placed caps ll of suitable material such as zirconium oxide or tungsten which provide good arcing surfaces, and the caps l1 and sleeves l6 are secured together in such manner as to provlde good heat conductivity therebetween. For example, these elements may be spot welded to one another at a plurality of points so as to provide good contact between their surfaces, or the tungsten may be electroplated on the nickel. The electrodes are supported at opposite ends of the tubes in any suitable manner as by means of supporting bands I 0, l8 and supports l9, is which are secured to said supporting bands in any suitable manner as by welding and are fused in the stem l4 and in the end of the bulb ll respectively.

Heating filaments are provided for each of the electrodes and said heating filaments are preferably connected together and with the electrodes insuch a way that a potential drop is impressed across the electrodes. In the form shown, the

filaments are connected in series with one an-- other and with the filament 6 and the electrodes are connected directly across the heating filaments so that the arc path is in parallel therewith. A wire 20 connected to one end of the filament 6 leads to the support It and thence through the wall of the bulb ii to a filament 2| within the upper electrode. The other end of filament 2| is connected by a wire 22 with a resistance 23 external to the bulb II, and a wire 24 connects said resistance with one end of a filament 25 positioned within the lower electrode. The other end of filament 25 is connected by a wire 26 with the support I! and further by means of a wire 21 and one of the supports IS with the lead 5. The filaments 2| and 25 may be insulated from the electrodes l8 and I! in any suitable manner, as by coating said filaments with an insulating cement. 7

When current is supplied to the lamp, it flows through a series circuit in the lamp comprising the lead 4, support I, filament 6, wire 20, filament 2|, resistance 23, filament 25,'wires 26and 21, and lead 5. The filament 6 immediately heats up and provides a source of visible radiation. At the same time the filaments 2| and 25 heat'the electrodes together with the oxide coatings I6.

The mercury or other-gas or vapor within the bulb in is ionized by the heat from the filaments and by the electronic emission from the oxide coatings and since a potential diiference is maintained between the electrodes, an arc strikes between them. The tungsten arcing surfaces of the electrodes also heat up rapidly and the are 7 establishes and maintains itself between the tungsten caps. As soon as the arc strikes, most of the current fiows through the arc path and filaments 2| and 25 tend to cool oil thereby reducing the amount of energy dissipated in these filaments during normal lamp operation. The resistance may not be necessary in all cases, but may be added where desired to increase the potential difference between the electrodes which is available for starting the are. As shown the resistance 23 is external to the bulb l I so that there is no danger of the are striking thereto. If positioned within the arc chamber, the resistance should be insulated in some manner as by coating it with a suitable insulating cement.

Fig. 3 illustrates another form of electrode embodying the invention. In this figure, the electrode comprises a tube 28 having one end closed at 29, said tube being'formed of material suitable for the arcing surface such as tungsten. Over the lower end of the tube 28 is positioned a sleeve 30 of nickel or the like which carries a coating ll of oxides for starting the are. As described above, the tube 28 and the sleeve 30 should be secured together in such a manner as to provide good heat conduction as for example by spot welding or by electroplating the nickel on the timgsten. This electrode may be mounted in the arc cham- 'ber in any suitable manner, as by a support 82' welded or otherwise secured to the sleeve 30 and fused in a stem 33 similar to the stem l4 described above.

Fig. 4 illustrates another arrangement of electrodes, the electrodes themselves being of the form shown in Fig. 3 although the electrodes shown in Fig. 2 are equally well adapted for this arrangement. In Fig. 4, the electrodes are placed at an angle to one another instead of end to end as shown in Fig. 2, the tungsten arcingsurfaces being close together and the oxide coated ends of the electrodes being relatively apart. With this arrangement the arc strikes initially between the oxide coated ends of the tubes and then transfers itself to the tungsten arcing surfaces. The means. for supporting these electrodes and the wiring connections for the heating filaments and electrodes may be similar to those shown in Fig. 2.

Where the lamp is to be used for therapeutic purposes, it is desirable that the material of the bulbs I and ll be capable of transmitting ultraviolet radiation. It is known that the most valuable radiations of the ultra-violet spectrum are of wave lengths longer than 2800 to 2900 Angstrom units and that shorter wave lengths are objectionable and may produce harmful effects. Hence the material of the bulbs need only transmit radiations down to these limits. Ultra-violet glasses having such filtering characteristics are known, an example being the special glass known as corex. All of the filtering may, however, be done at the inner bulb since the incandescent filament .6 will not at normal temperatures emit radiations short enough to be objectionable. To this end the inner bulb may be provided with a liner 34 of some filtering material such as mica One advantage of the arrangements shown in Figs. 1 to 3 inclusive, wherein the electrodes are arranged end to end in the bulb, is that in case any deposit tends to form in the bulb, the accelerating potential is in such a direction that the deposit forms in-the ends of the bulb. That is, the accelerating potential acts lengthwith of the bulb and drives any vaporized material in the bulb toward one or the other end, leaving the central part clear where the arc illumination is most effective. Fig. 5 shows a particular arrangement which takes advantage of this action. In this figure, the electrodes 3! and 36 may be of either form shown in Figs. 1 to 3 or of any other suitable type, and the electrical connections may also be arranged as shown in Figs. 1 to 3 or in any other suitable way. The bulb is provided with an enlarged central portion 31 and with two opposed wells or end chambers 30 and 39 in which the electrodes 35 and I! are positioned. Since the arc strikes between the electrodes, the accelerating potential acts toward one or the other of the electrodes and if there is any tendency toward deposition on the walls of the bulb, the deposit will form in the chambers 36 and 39 leaving the central chamber 31 clear for illumination.

While several embodiments of the invention have been described and illustrated in the drawing, it will be understood that the invention is not limited to these particular forms but is capable of a variety of mechanical expressions while changes may also be made in the form, details of construction and arrangement of the parts without departing from the spirit of the invention. Moreover, the use of electrodes is not restricted to the particular type of lamp shown. For example, it may be desired to use the arc element alone without the incandescent filament 8 or the electrodes themselves may be employed in any electric arc lamp for which they are suitable. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. An electrode for use in electric arc lamps comprising a metallic sleeve having a portion coated with oxide capable of electronic emission when heated for starting the are, a protecting cap covering another portion of said sleeve and adapted to maintain the are after starting, said cap being formed of conductive material different from and more resistant to disintegration on are operation than the metal from which said sleeve is formed, and a heating filament within said sleeve.

2. An electrode for use in electric arc lamps comprising a nickel tube coated with an oxide having high electronic emission when heated for starting the arc, a protecting cap for the end of said tube adapted to maintain the arc after starting, said cap being formed of highly refractory material different from and more resistant to disintegration on are operation than nickel, and a heating filament within said tube and cap.

3. An electrode for use in electric arc lamps comprising a platinum tube coated with an oxide having high electronic emission when heated for starting the are, a protecting cap for the end of said tube adapted to maintain the are after starting, said cap being formed of highly refractory material different from and more resistant to disintegration on are operation than platinum, and a heating filament within said tube and cap.

4. An electrode for use in electric arc lamps comprising a nickel sleeve having a portion coated with oxide having electronic emission. a

tungsten cap covering one end of said sleeve, and a filament within said sleeve.

5. An electrode for use in electric arc lamps comprising a tungsten sleeve closed at one end,

a nickel sleeve surrounding the other end, said sleeves being secured together to provide heat conductivity therebetween, and a coating of elecportion of said sleeve adjacent the open end comprising nickel and being coated with oxide having electronic emission.

8. An electric arc lamp comprising a bulb, a pair of arc electrodes therein each comprising a metallic sleeve closed at one end and open at the other end, the closed ends being of tungsten and constituting arcing surfaces, a portion of said sleeves adjacent their open ends being of nickel and coated with oxide having electronic emission, said electrodes being disposed end to end in said bulb with their closed ends adjacent, a heating filament in each electrode, connections from said filaments to said electrodes, and means for energizing said filaments.

9. An electric arc lamp comprising a pair of electrodes of zirconium oxide disposed with portions thereof closely adjacent and other portions thereof relatively remote, said closely adjacent portions constituting arcing surfaces and said remote portions including an oxide having high electronic emission when heated, means for heating said electrodes, and means for energizing said electrodes.

10. An electric arc lamp comprising a pair of hollow electrodes of zirconium oxide disposed with portions thereof closely adjacent and other portions thereof relatively remote, said adjacent portions constituting arcing surfaces and said remote portions including an oxide having high electronic emission when heated, heating filaments within said electrodes, and means for energizing said filaments and electrodes.

11. An electrode for use in electric arc lamps comprising a metallic sleeve closed at one end and opened at the other, a portion of said sleeve adjacent the open end being coated with an electron-emissive oxide for starting the arc and the closed end having an exterior surface for carrying the are after starting formed of highly refractory conductive material different from and more resistant to disintegration on are operation than the metal from which the sleeve is formed.

12. In electric arc lamps, means for establishing an arc comprising a pair of tubular electrodes each being closed at one end and open at the other and having an arc-starting portion adjacent its open end made of a metal having an affinity for and coated with an electron-emitting oxide, the closed end of said electrodes constituting an arecarrying portion and formed of a conductive material different from and more resistant to dis- 4 a,oos,ess

and s protecting cap for the end at soid sleeve formed of a conductive material diilerent from and more resistant to disintegration on are operation than the material of said sleeve selected from the group consisting of tungsten and zirconium l oxide.

GEORGE SPERM.- 

